Solar wind flowing from this coronal hole could reach Earth on Feb. 18. However, the solar wind stream is likely to sail south of our planet, making little impact. Credit: SDO/AIA.

SPACE WEATHERNOAA Forecasts

Updated at: 2012 Feb 17 2200 UTC

FLARE

0-24 hr

24-48 hr

CLASS M

01 %

01 %

CLASS X

01 %

01 %

Geomagnetic Storms:Probabilities for significant disturbances in Earth's magnetic field are given for three activity levels: active, minor storm, severe storm

Updated at: 2012 Feb 17 2200 UTC

Mid-latitudes

0-24 hr

24-48 hr

ACTIVE

30 %

30 %

MINOR

15 %

15 %

SEVERE

01 %

01 %

High latitudes

0-24 hr

24-48 hr

ACTIVE

40 %

40 %

MINOR

20 %

20 %

SEVERE

05 %

05 %

Friday, Feb. 17, 2012

What's up in space

Don't just watch shooting stars. Wear them! Authentic meteorite jewelry for Valentine's Day is now available in the SpaceWeather Store.

SUNSET PLANETS: The brightest planets in the night sky are aligning for a must-see show in late February and March 2012. You can start looking tonight. [video] [full story].

AURORA WHIRLPOOL: On Feb. 14-15, Arctic skies erupted with an unexpected display of auroras that veteran observers said was among the best in months. At the height of the event, a US Defense Meteorological Program satellite photographed a whirlpool of Northern Lights over the Bering Sea:

"A number of images from the DMSP F18 satellite captured the dramatic auroral event of the last couple nights," says analyst Paul McCrone, who processed the data at the US Navy's Fleet Numerical Meteorology and Oceanography Center in Monterey, CA.

The reason for the outburst is still not completely clear. It started on Feb. 14th when a magneticdisturbance rippled around the north pole. No CME was obvious in local solar wind data at the time; the disturbance just happened. Once begun, the display was amplified by the actions of the interplanetary magnetic field (IMF). The IMF near Earth tipped south, opening a crack in our planet's magnetic defenses. Solar wind poured in and fueled the auroras. Geomagnetic storm alerts:text, voice.

SPY-SAT DISAPPEARING TRICK: US spy satellite Lacrosse 5 occasionally confounds observers by disapppearing: In a matter of seconds, it can fade more than three astronomical magnitudes. Is this a deliberate form of stealth? Most experts think not, but no one outside of classified circles knows for sure what is going on.

To investigate, French astrophotographer Thierry Legault used his satellite-tracking telescope to photograph Lacrosse 5 as it sailed 490 miles above Paris on Jan. 15, 2012, and he caught the spysat in the act of disappearing:

"During the passage, the brightness of the satellite decreased by 10 times in only 4 seconds (a loss of 2.5 magnitudes)," describes Legault. "After 33 seconds of [dark flight] it regained its original brightness. Lacrosse 5 often shows this very singular behaviour, which is called by other observers (especially Marco Langbroek) the 'disappearing trick.'"

Other Lacrosse satellites do not perform the same trick, at least not to this extent, suggesting that the design of Lacrosse 5 differs from its predecessors. The fade is likely caused by some sort of self-shadowing--e.g., maybe some part of the spacecraft such as its solar panels casts a shadow over the main body when the spysat changes attitude.

Even Legault's fine images do not reveal the answer. "The cause of the disappearing trick, as well as the precise shape of the satellite, remain unknown."

Potentially Hazardous Asteroids (PHAs) are space rocks larger than approximately 100m that can come closer to Earth than 0.05 AU. None of the known PHAs is on a collision course with our planet, although astronomers are finding new ones all the time.